In the production of petroleum from subterranean strata, it is often necessary to drill a well bore through several distinct areas or levels of potential petroleum production. After the exhaustion of the producing strata at the base of the well bore, it has been common practice to attempt to recover producing strata at an intermediate portion of the well bore. A problem exists in recovering an intermediate petroleum strata level because of the fact that the well bore contains a metal casing which is backed by cement or concrete. In order to recover such intermediate strata levels, it has become necessary to perforate the well casing and the concrete and surrounding strata to allow access of any liquid reserves into the well bore. The desired level of subsequent recovery at intermediate strata levels is often several thousand feet below the surface of the well head. This requires the use of remotely operated equipment which is of a sufficient compact arrangement as to be acceptably used and retrieved from the well bore.
Alternately, in the production of petroleum from offshore petroleum reserves, it is sometimes necessary to completely cut and remove stringers or pipes at the sea floor after termination of the recovery operation offshore. Cutting is also necessary to retrieve pipe and downhole tools from both land-based and offshore well bores.
Various methods and apparatus have been considered in the cutting and perforating of well casings at or below the level of the well head. These systems include the firing of bullets or slugs into the well casing, the explosion of charges which impel non-bullet masses into the well casing, the use of various chemical cutters such as fluorine and bromine trifluoride and undersea cutting torches.
The use of fluorine as an oxidizing agent for the production of a hot flame in metal cutting per se is well known in the prior art as evidenced by U.S. Pat. No. 2,421,649 wherein a cutting torch is fueled with hydrogen and fluorine.
Chlorine trifluoride is also a known oxidizer which can be used with hydrogen and hydrocarbon gases to provide a metal cutting flame as taught in U.S. Pat. No. 2,642,656.
In U.S. Pat. No. 2,918,125, the use of various fluorine compounds is set forth for the cutting of apparatus such as the wall of a well. The chemical cutting agents include fluorine and various halogen fluorides such as chlorine trifluoride, chlorine monofluoride, bromine trifluoride, bromine pentafluoride, iodine pentafluoride and iodine heptafluoride.
Other halogen fluorides are also known to be used as metal cutting agents as suggested in U.S. Pat. No. 3,066,058 wherein perhalogenyl fluoride is disclosed as a cutting or welding agent per se.
U.S. Pat. No. 3,071,852 discloses the use of nitrogen trifluoride as an oxidant to be mixed with a suitable reducing gas for a welding torch or alternately the use of nitrogen trifluoride by itself as a cutting gas per se.
The various bullet or explosive cutting and perforating methods for opening well casings are set forth in PRODUCTION OPERATIONS, Volume 1, Chapter 7, Perforating Oil and Gas Wells, Pages 187-202.
However, despite the numerous attempts to design a method for down-hole perforating of a well casing and the surrounding concrete and earth strata or the cutting of downhole tools and offshore stringers, various drawbacks persist such as the danger of explosion of highly reactive compounds, the misdirection and lack of penetrating power of metal slugs, and the failure of compounds such as bromine trifluoride to cut or perforate concrete and rock strata. The present invention overcomes these drawbacks by providing a safe stable chemical cutter or perforator which provides a highly reactive supply of a chemical cutter or perforator which successfully cuts or perforates metal, concrete and rock strata.